Wirth Completes Shaft II in Sedrun for Gotthard Base Tunnel in Record TimeThe breakthrough by a Wirth shaft boring machine of the tunnel floor level on 23rd June, 2003 marked another milestone at the Gotthard base tunnel. The about 800 m-deep 7 m-diameter shaft Sedrun II has been completed in the record time of 12 months by Thyssen Schachtbau in JV with its Austrian affiliate Östu-Stettin and its South African partner RUC Mining Contractors Ltd. The shaft is part of the Sedrun intermediate drive. The remarkable achievement took place in extremely difficult geology.The construction of a second vertical shaft was necessary in Sedrun for logistical and safety reasons. In an initial phase, a pilot hole was bored by means of a Wirth type HG 330-SP raise borer from June 2002 to August 2002. Despite extremely difficult geological conditions which frequent alternating hard, tenacious and soft rock formations and collapsing layers, the deviation of the shaft axis was only 34 cm at the breakthrough point in the shaft basis cavern about 800 m deeper.After the breakthrough, the HG 330-SP reamed the pilot hole by applying the raise boring method upwards to 1.80 m in diameter. Equipment was subsequently installed within the shaft. In late January 2003, a Wirth shaft sinker type VSB VI started reaming downwards the raise borehole to the diameter of about 7 m. The average daily performance was about 6 m. Simultaneously with the boring operation, the shaft was lined with a 22 cm-thick single-coat steel-fibre shotcrete layer. The Sedrun intermediate drive is approximately 1,400 m above sea level. Work was frequently hampered by extreme winter weather conditions, debris avalanches and rockfalls. When finished in 2012, the Gotthard base tunnel will be the longest tunnel in the world. Visit www.wirth-europe.de/NEWS/Gotthard_Tunnel.htm and www.alptransit.ch/pages/e/index.php. Read E-News Weekly 29/2003. 31/03. Wirth's shaft sinker VSB VI breaking through shaft II in Sedrun.   Wirth shaft sinker VSB VI at the workshop.